New (S=1) EPR AA17 center in silicon - microplatelets or precursor of platelets?

New (S = 1) EPR spectrum (labeled Si-AA17) is observed in irradiated high-p urity hydrogen-contained silicon after annealing at greater than or equal t o 200 degrees C. The AA17 defect has D-3d symmetry with g(\\) = 2.0028, g(p erpendicular to) = 2.0106; A(\\)(Si-29) = 175.0 MHz, A(perpendicular to) = 89.0 MHz; and D-\\ = +/- 33.6 MHz, D-perpendicular to = +/- 16.8 MHz. It is paramagnetic in a neutral charge state. An analysis of Si-29 hf interactio n has shown that 62% of the resonant wave function belong to two equivalent silicon atoms. The magnitude of zero-field splitting (D = 16.8 MHz) of AA1 7 has a smallest value among the known (S = 1) EPR centers in silicon and i ndicates that the distance between two equivalent Si sites (spins) creating the S = 1 state, is similar to 12 Angstrom along to (111) axis. Most suita ble model of the defect is the {111} planar hexavacancy situated between tw o (111) dangling Si bonds separated. by similar to 12 Angstrom. Each of the se dangling bonds is formed as a result of saturation of the nearest Si ato m by one hydrogen located at AB position. (C) 2000 Elsevier Science S.A. Al l rights reserved.